The technology of the present disclosure relates to a fixing device and an image forming apparatus including the same.
Conventionally, as a fixing device mounted in an electrophotographic image forming apparatus, there has been known a fixing device including an endless fixing belt, a heating body, and a pressing roller. The heating body abuts an inner peripheral surface of the fixing belt and the pressing roller abuts an outer peripheral surface of the fixing belt. The pressing roller is brought into press-contact with the heating body while interposing the fixing belt between the pressing roller and the heating body. In this state, the pressing roller is driven by a motor, so that the fixing belt is rotated. In the fixing device, a paper passes through between the fixing belt and the pressing roller, so that a toner image is fixed to the paper. According to this, since a fixing member for fixing a toner to a paper is configured with a belt member with a thin thickness, heat dissipation of the fixing member is enhanced, so that it is possible to prevent an offset phenomenon of a toner.
In this type of fixing device, there is a case in which the fixing belt slips with respect to the pressing roller, so that the rotation speed of the fixing belt is reduced or the fixing belt stops. As a consequence, there is a problem that a predetermined part of the fixing belt is locally heated by the heating body and thus the belt is broken.
In this regard, there has been proposed a fixing device which detects the temperature of the fixing belt by a thermistor, and determines slip abnormality when the rate of change of the detected belt temperature according to the passage of time exceeds a predetermined threshold value.